Measuring the baryon acoustic oscillation peak position with different galaxy selections

Abstract

We investigate if, for a fixed number density of targets and redshift, there is an optimal way to select a galaxy sample in order to measure the baryon acoustic oscillation (BAO) scale, which is used as a standard ruler to constrain the cosmic expansion. Using the mock galaxy catalogue built by Smith et al. in the Millennium-XXL N-body simulation with a technique to assign galaxies to dark matter haloes based on halo occupation distribution modelling, we consider the clustering of galaxies selected by luminosity, colour and local density. We assess how well the BAO scale can be extracted by fitting a template to the power spectrum measured for each sample. We find that the BAO peak position is recovered equally well for samples defined by luminosity or colour, while there is a bias in the BAO scale recovered for samples defined by density. The BAO position is contracted to smaller scales for the densest galaxy quartile and expanded to large scales for the two least dense galaxy quartiles. For fixed galaxy number density, density-selected samples have higher uncertainties in the recovered BAO scale than luminosity-or colour-selected samples.

Estimating Galactic Dark Matter and Redshift in Flat Space Cosmology

“…It may be noted that, according to Baryonic acoustic oscillations, current galactic separation distance is around 490 million light years [21,22]. In this context, relation (16) can be recommended for further research.…”

“…Based on the two curves presented in Figure-2, it is certainly possible to say that, if 'light travel distance' is a characteristic index in Lambda cosmology, the same index, can also be understood with our re-defined red shift relation (19) and 'light speed expansion'. Relation (22) indicates that, for increasing light travel distances, c z seems to have higher values compared to re-defined redshift n z . See Figure 3.…”

“…Red curve indicates our re-defined redshift and green curve indicates traditional redshift. To some extent, based on relations (21) and (22), it is possible to guess that, currently believed cosmic acceleration can be considered as an alternative interpretation associated with the alternative relation (20). It needs further study with respect to galactic redshifts and star rotation curves etc.…”

“…In this context, based on the data presented in Table 2, our proposed definition of Redshift i.e. relations (20) and (22) can be recommended further research. 13) Quantum cosmology point of view, Lambda cosmology needs a review at fundamental level.…”

Applications of current cosmic angular velocity

“…At any stage of expansion, we assume that, Proceeding further, considering current cosmic radius as a scaling length and by considering average flat rotation speed of any two neighboring galaxies, their separation distance (as expected by Baryonic Acoustic Oscillations) [19,20] can be fitted with a relation of the…”